creation date: 2026-06-09 02:08
tags: Pathologies
Non-Arteritic Anterior Ischemic Optic Neuropathy
Background
Definitions
Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common form of ischemic optic neuropathy. This is a common optic nerve disorder for patients >50 years of age.
Relevant Anatomy
The optic nerve head is supplied by 15-20 short posterior ciliary arteries from the ophthalmic artery and arterial branches from the circle of Zinn-Haller.
The vascular supply may be split into upper and lower halves, that may manifest with altitudinal damage from ischemia.
The retina is supplied by the choroidal circulation and branches from the central retinal artery, which derive from the ophthalmic artery.
Etiology and Risk Factors
Atherosclerosis
AS is strongly associated with NAION. Risk factors include:
- Hypertension
- Smoking
- Diabetes
- Hyperlipidemia
Other conditions
- Nocturnal hypotension
- Prothrombotic abnormalities
- Ocular risk factors (small physiologic cup, cataract/other eye surgeries)
- Obstructive sleep apnea
- Kidney failure
Medications
Links between medications and NAION are not clear. Possible associated medications are:
- PDE-5 inhibitors
- GLP-1 agonists
- Interferon-alpha
- Amiodarone
- Sympathomimetics
Pathogenesis
NAION occurs due to acute ischemia to the optic nerve head. The exact mechanism to optic disc ischemia is unclear but evidence suggests a combination of:
- Atherosclerotic risk factors
- Mechanical obstruction of optic head nerve and thus axoplasmic flow
- Occlusion of tributaries of central retinal vein leading to nerve head edema and secondary arteriolar constriction
Clinical Presentation
Signs & Symptoms
Vision loss is typically described as:
- Monocular (90%; bilaterally only in cases of severe blood pressure fluctuations)
- Occurring over hours to days (average peak vision loss at 5 days)
- May present upon awakening (40-70%)
- Without prodrome
- Painless
Examination may demonstrates:
- Reduced visual acuity (ranges from 20/20 to no light perception)
- Dyschromatopsia (reduced colour vision; prevalent in almost all)
- Relative afferent pupillary defect
- Optic disc edema
- Peripapillary splinter hemorrhage
- Small optic cup
History & Physical Exam
History should include:
- Pattern of vision loss
- Onset and characteristics
- Atherosclerotic risk factors and associated conditions
- Ruling out of giant cell arteritis (eg. questions regarding headache, scalp tenderness, jaw claudication)
History should include neurologic exam and fundoscopy.
Diagnosis
Criteria
Diagnosis is made clinically based on:
- Characteristic age (>50)
- Presence of vasculopathic risk factors (smoking, hypertension, diabetes)
- Pattern of vision loss
- Characteristic findings on fundoscopy (swollen disc)
Work-up
Ruling out GCA
Arteritic ischemic optic neuropathy (eg. giant cell arteritis) should be considered.
- ESR/CRP
- Temporal artery biopsy if ESR/CRP elevated or clinical suspicion
Further workup for atypical features
Neuroimaging (contrast MRI) may be indicated if atypical features are present:
- Age <50
- Absence of risk factors
- Large cup-to-disc ratio in unaffected eye
- Hemianopic visual field loss
- Bilateral simultaneous or rapidly sequential anterior ischemic optic neuropathy
- Transient visual loss preceding visual loss
- No optic disc edema in acute phase
- Progression after two to four weeks
- Recurrence in same eye
- Inflammation in anterior or posterior segment of eye
- Optic atrophy at presentation
- Pain on eye movement
Differential
NAION must be differentiated from other optic neuropathies:
- Giant cell arteritis
- Optic neuritis (differentiate: pain on eye movement, younger patients)
- Leber hereditary optic neuropathy (differentiate: younger patients, no swelling, central defect, male dominated)
- Neuroretinitis (differentiate: children, bilateral)
Red Flags / Complications
See work up section on atypical features for red flags.
The major complication is progression of vision loss. Most patients stabilize after initial period but some worsen. Recovery of visual fields is unlikely.
Recurrence and contralateral events are not common.
- <6% same-eye recurrence rate at two years
- 15% contralateral cumulative risk over five years
Management
There is no proven therapy. Generally, patients should undergo:
- Blood pressure management (both correct hypertension and systemic hypotension)
- Management of atherosclerotic risk factors
While there is no proven benefit, long-term aspirin therapy may be appropriate based on other risk factors and comorbidities.